JP2002029822A - Hollow ceramic sintered body, sliding member using the same, and ceramic bearing ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow ceramics sintered compact suitable for a sliding member, particularly for a bearing ball for electronic appliances such as a hard disk drive. SOLUTION: In the hollow ceramics sintered compact having an internal hollow, when a straight line is drawn in the thickness direction of the sintered compact, 5-60% of electric conductivity imparting particles are allowed to exist on the straight line. The sliding characteristics and crushing strength of the sintered compact are enhanced by controlling the distance between electric conductivity imparting particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow ceramic sintered body having a hollow portion. The present invention relates to a hollow ceramic sintered body. And a ceramic bearing ball.

[0002]

2. Description of the Related Art In recent years, hard disk drives (HDDs)
Electronic devices such as magnetic recording devices, optical disk devices or DVDs, and various game devices have been remarkably developed.
These generally function various disks by rotating the rotating shaft at high speed by a rotary drive device such as a spindle motor. Conventionally, metal such as bearing steel has been used for a bearing member for supporting such a rotating shaft, for example, a bearing ball. However, metals such as bearing steel do not have sufficient wear resistance.
In the field where high-speed rotation of 5000 rpm or more is required, there is a large variation in life, and it has not been possible to provide a reliable rotation drive. In order to solve such a problem, in recent years, a silicon nitride sintered body has been used for a bearing ball. Since the silicon nitride sintered body has excellent sliding characteristics among ceramics, it has sufficient abrasion resistance, and can provide a reliable rotation drive even at high speed rotation.

[0003]

However, since the silicon nitride bearing ball is an electrically insulating material, the static electricity generated when rotating at a high speed is rotated by a rotating shaft formed by a metal member such as bearing steel. It has been found that a problem arises in that static electricity is not easily dissipated to members and ball receiving members (so-called bearing members other than bearing balls). If the static electricity is not sufficiently dissipated and charged more than necessary, electronic devices, for example, a recording medium using a magnetic signal, such as a hard disk drive, are adversely affected, and as a result, the electronic device itself, such as a hard disk, itself. The phenomenon which said that it destroyed was confirmed. As bearing balls, oxide ceramics such as aluminum oxide and zirconium oxide have conventionally been used for general machine tools. However, since these are also insulators, they cannot prevent electrostatic charging. Also, electronic devices such as portable personal computers,
Electronic notebooks, various mobile products, and the like are becoming smaller and lighter year by year, and demands for smaller and lighter spindle motors are increasing with the demand for higher capacity and smaller size of hard disks used therein. For example, in order to increase the capacity and reduce the size of a hard disk, it is necessary to rotate the disk at a high speed. In the near future, a high-speed rotation of about 10,000 rpm or more is expected. Usually, the bearing member that supports such high-speed rotation is a rotating shaft member, a bearing ball, and a ball receiving member, and the stress during rotation is substantially concentrated on the bearing ball.

[0004] The stress at the time of rotation is related to the weight of the bearing ball itself, and the stress generated at the time of rotation changes according to the weight of the bearing ball. Therefore, it is desired that the bearing ball is light and has good sliding characteristics. In particular, bearing members used as sliding members for electronic equipment and bearing balls are different from the use environment where severe vibrations and pressures are applied like general machine tools, so they always have the same crushing strength as bearing balls for general machine tools. Is not necessary. Therefore, for electronic devices, if the sliding characteristics are equivalent, it is possible to contribute to a reduction in the weight of the bearing member and further to a reduction in the weight of the electronic device, even if the crushing load is somewhat inferior, even if the load is low. The present invention has been made in order to solve the above-described problems.Since it has a hollow portion, it is possible to reduce the weight, and more than necessary by providing a predetermined amount of conductive particles. An object of the present invention is to provide a sliding member suitable for an electronic device such as a hard disk drive, for example, a bearing ball because it can prevent static electricity from being charged.

[0005]

The hollow ceramic sintered body of the present invention is a ceramic sintered body having a hollow portion inside, and when a straight line is drawn in the thickness direction of the ceramic sintered body, a conductive line is formed on the straight line. It is characterized in that 5 to 60% of the particles for imparting properties are present. Further, the hollow ceramic sintered body preferably has an electric resistance value of 10 ⁹ to 10 ² Ω · cm. In order to make the electric resistance value a predetermined value, it contains conductivity imparting particles, and the distance between the conductivity imparting particles is 0.
It is preferable that it is within the range of 10 μm. Further, the hollow ceramic sintered body of the present invention is preferably spherical.

The ceramic sintered body is zirconium oxide,
It is preferable that at least one of aluminum oxide and silicon nitride is the main component.
It is preferably at least one of carbides or nitrides of i, Nb, Hf, W, Mo, Ta, Cr, Zr, Mn, and B. Further, such a hollow ceramic sintered body of the present invention is suitable for a sliding member, and is particularly suitable for a sliding member for electronic equipment. Examples of the sliding member for an electronic device include a bearing ball used for a bearing portion of a spindle motor.

For example, in the case of a bearing ball, the size of the hollow portion is preferably 以下 or less (50% or less) with respect to the radial direction of the ceramic bearing ball.
The hollow ceramic sintered body of the present invention has an electrical resistance of 10 ⁹ to 10 ² Ω
cm, so that when applied to a bearing ball of a bearing member used in a spindle motor of a hard disk drive, for example, as a sliding member for an electronic device, it is possible to prevent static electricity generated by rotation driving from being unnecessarily charged. Becomes In addition, since it has a hollow portion, it is possible to reduce the weight without deteriorating the sliding characteristics as compared with the one having no hollow portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a hollow ceramic sintered body, a sliding member using the same, and a ceramic bearing ball of the present invention will be described. FIG. 1 is a sectional view of a ceramic bearing ball showing one example of the hollow ceramic sintered body of the present invention. In FIG.
1 ceramic surface portion, 2 a hollow portion, R ₀ is the radius, R ₁ is shows the thickness of the ceramic surface layer portion to the radius.

In the hollow ceramic sintered body of the present invention, when a straight line is first drawn in the thickness direction of the sintered body, the straight line (R ₁
The above is characterized in that the conductivity imparting particles are present in 5 to 60%. This is to mean that the conductivity-imparting particles to the length of R ₁ is present 5% to 60%. By adopting such a configuration, a hollow ceramic sintered body having an electric resistance value of 10 ⁹ to 10 ² Ω · cm and also having excellent sliding characteristics, and a sliding member using the same can be manufactured. Can be obtained.

When the proportion of the particles imparting conductivity is less than 5%, the electric resistance exceeds 10 ⁹ Ω · cm, and the effect of the addition cannot be substantially obtained. With such a high electric resistance value,
For example, when applied to a bearing ball used for a spindle motor for driving a hard disk drive,
The static electricity generated by the rotation drive cannot be dissipated satisfactorily, causing a problem in the hard disk.

On the other hand, if it exceeds 60%, the number of conductive particles in the ceramic sintered body becomes too large, and the bonding force between the ceramic matrix particles is weakened, so that the strength of the ceramic sintered body is reduced.

Accordingly, on the straight line when a straight line is drawn in the thickness direction is preferably (R ₁ above) to the conductivity imparting particles is in the form that is present from 5% to 60%, even more in the range of 20-50% It is preferred that Within the range of 20 to 50%, the electric resistance can be easily controlled to 10 ⁶ to 10 ³ Ω · cm.

[0013] Incidentally, taking the hollow ceramic sintered body enlarged photograph of 1,000 times or more the part corresponding to R ₁ of the drawing lines in the thickness direction, pulling the following linear thickness 0.5 mm, even a little on the straight line All touching conductivity imparting particles shall be counted. In FIG. 1, a spherical hollow ceramic sintered body has been described. However, even in the case of an elliptical shape, a cylindrical shape, a prismatic shape, etc., similarly, a radius R ₀ is taken at each central portion in a cross section, and the radius It can cope by counting the ratio of the conductive imparting particles on R ₁ to.

Up to this point, the thickness R _{1 of the} ceramic surface layer has been described.
Although the number of the conductivity-imparting particles in the above has been described, in the present invention, the distance of each of the conductivity-imparting particles is preferably in the range of 0 to 10 μm, and more preferably 1 to 5 μm. The individual distances conductivity imparting particles is that the distance on R _1. In other words, the distance between the conductive particles is defined in the thickness direction of the hollow ceramic sintered body.

A distance of 0 μm between the individual conductivity-imparting particles indicates that there is a portion where the conductivity-imparting particles are in contact with each other. If there is a contact, the conductivity can be improved and the electric resistance value can be reduced. However, if the conductivity-imparting particles are in contact with each other in many cases, the conductivity-imparting particles are condensed and eventually become a fracture starting point, which causes a reduction in the strength of the ceramic sintered body. Therefore, if the state where the conductivity-imparting particles each distance on R ₁ are in contact with 0μm exists, its prevalence is 50% or less on R _1, more preferably not more than 20%.

On the other hand, the distance between each of the conductive particles is 10 μm.
If it exceeds, the effect of lowering the electric resistance value becomes small, and it cannot be said that it is very good. In such a case, it is conceivable to add the conductivity-imparting particles more than necessary or to increase the size of the conductivity-imparting particles more than necessary, but in any case, the strength of the ceramic sintered body is reduced. . From this point of view, the maximum diameter of the conductivity-imparting particles is apt to cause a decrease in strength when the maximum diameter of the conductivity-imparting particles is too large. It can be said. Various particles such as particles, whiskers, and fibers can be used as the conductivity imparting particles as long as they satisfy the above-mentioned maximum diameter, but are preferably in the form of particles. Since the hollow ceramic sintered body of the present invention is mainly used for a sliding member, the surface of the sintered body naturally becomes a sliding surface. At this time, the conductivity-imparting particles are also present on the sliding surface, and if the conductivity-imparting particles are whiskers or fibers, the thorns present on the surface are likely to become fracture starting points. The maximum diameter of the conductivity-imparting particles indicates the longest diagonal line of the conductivity-imparting particles.

[0017] Thus, the ratio is 5% to 60% of the conductivity imparting particles on the thickness direction R ₁ of the hollow ceramic sintered body, the distance between the conductive imparting particles 0～10Myuemu, the maximum diameter of the conductive imparting particles 5
The most preferred form is less than μm.

Next, the material will be described. Ceramics forming the matrix include zirconium oxide,
At least one of aluminum oxide and silicon nitride or 2
Preferably, it consists of more than one species. Both matrix ceramics have high electrical resistance of 10 ¹⁰ Ω · cm or more, but have excellent sliding properties and strength, and are suitable for sliding members. The electrical resistance value of the conductivity imparting particles is 10 ⁷ Ωcm
It is not particularly limited as long as it is the following, for example,
Examples include at least one of carbides, nitrides, and borides of 4a group, 5a group, 6a group, 7a group, 8 group, Si and B. In particular, S
Preferred are carbides or nitrides of i, Ti, Nb, Hf, W, Mo, Ta, Cr, Zr, Mn, and B. As described above, the hollow ceramic sintered body of the present invention is mainly used for a sliding member, and there is also a conductivity-imparting particle on the sliding surface. Characteristics are required. The above-mentioned carbides or nitrides have particularly excellent sliding properties, so that the electrical resistance of the hollow ceramic sintered body can be reduced to 10 ⁹ Ωcm or less and the sliding properties of matrix ceramics can be maintained. I do.

Although the hollow ceramic sintered body of the present invention comprises matrix ceramics and particles for imparting conductivity, it goes without saying that other components may be added. Other components include, for example, sintering aids such as rare earth oxides and alkaline earth metal oxides, and the content is not particularly limited, but is preferably in the range of 2 to 15% by weight.

Such a hollow ceramic sintered body of the present invention is suitable for a sliding member. Examples of the sliding member include sliding members for electronic devices. Examples of the electronic device include a magnetic recording device such as a hard disk drive, an optical disk device such as a DVD, a magneto-optical device, various game devices, and medical devices. As sliding members used for such electronic devices, there are a bearing member used for a motor for rotating various disks, a sliding member used for each movable portion, and the like.

As the bearing member used for the motor, various bearing members such as a radial bearing, a pivot bearing, a dynamic pressure bearing and the like can be mentioned. For example, a radial bearing includes a rotating shaft, a bearing ball, and a ball receiving portion. The rotating shaft, bearing balls and ball bearings are often formed of metal such as ceramics or bearing steel, and the most commonly used form is to form the bearing balls with ceramics and the rotating shaft and ball bearings with bearing steel. .

When such a bearing member is applied to, for example, a spindle motor for driving a hard disk drive, which is an electronic device, static electricity is generated as the bearing ball slides on the rotating shaft and the ball receiving portion.
If the electrical resistance value of the bearing ball exceeds 10 ⁹ Ω · cm, this static electricity will not be satisfactorily dissipated to the rotating shaft and the ball receiving portion, and will be charged more than necessary. When such a charging phenomenon occurs, the hard disk drive is adversely affected, and the reliability of the hard disk is reduced. In particular, hard disks in recent years have increased capacity,
As the speed increases, the rotation speed becomes 5000 rpm or more, and 10,000 rpm
The rotation speed is increasing to over m and the adverse effect of static electricity becomes a serious problem. Since the bearing ball, which is a sliding member using the hollow ceramic sintered body of the present invention, contains the conductivity imparting particles in a predetermined form, the electric resistance value is 10%.
^{It is 9} to 10 ² Ω · cm, which makes it possible to prevent unnecessary charging of static electricity even at high speed rotation.

Further, since the bearing ball of the present invention has a hollow portion, its crushing strength is inferior to that of a bearing ball having no hollow portion. This is not a problem because the load applied to the bearing ball is smaller than that of the bearing ball. Rather,
By having the hollow portion, the weight of the bearing ball is reduced, so that the centrifugal stress accompanying the rotational drive is reduced, the contact stress on the bearing ball surface can be slightly reduced, and the rolling life can be improved. In particular, as the diameter of the bearing ball is reduced to 3 mm or less, and further to 2 mm or less, and the rotational speed is increased to 5000 rpm or more and 10,000 rpm or more, the rolling life is improved. From this viewpoint, it can be said that the bearing ball of the present invention is preferably used for electronic devices and has a diameter of 3 mm or less.

Next, the manufacturing method will be described. Although there is no particular limitation on the manufacturing method, for example, the following method is available. First, a mixed raw material powder containing a predetermined amount of matrix ceramic powder, a sintering aid powder, and conductivity imparting particles or a slurry containing the mixed raw material powder is prepared. At this time, each raw material powder needs to be uniformly mixed, and it is particularly important that the conductivity imparting particles are uniformly dispersed without agglomeration. In order to facilitate uniform mixing of the conductivity-imparting particles, it is effective to, for example, previously mix a matrix ceramic powder and a sintering aid powder, and mix the conductivity-imparting particles a plurality of times little by little. In particular, by mixing twice or three or more times and further mixing at intervals of 20 minutes or more at each mixing, the mixing of the conductivity-imparting particles in the raw material powder is better than mixing all the conductivity-imparting particles at once. It is possible to prevent aggregation of the conductivity-imparting particles in the step.

From the viewpoint of uniform mixing, the matrix ceramic powder and the sintering aid powder have an average particle size.
It is preferable to use a fine powder of 5 μm or less, more preferably 1 μm or less. Similarly, the maximum diameter of the conductive particles is 5 μm.
The following is preferred.

Next, a core corresponding to the hollow portion is prepared by using an organic substance such as synthetic resin or plastic, and the core is used as a center to prepare a pre-rolled powder using the mixed raw material powder (or a slurry thereof) by a rolling granulation method. A molded body is produced. After performing a hydrostatic pressure press on the preformed body, degreasing and sintering are performed to burn out a core made of an organic substance, thereby making it possible to manufacture a hollow ceramic sintered body.

In the degreasing step, it is preferable to degrease while applying pressure at a pressure higher than the atmospheric pressure. When using the tumbling granulation method, the core component made of organic matter must be burned off.If the organic matter remains in the hollow part without being burned out, the core component is decomposed by the heat generated when the bearing ball slides. It will adversely affect the bearing ball. In particular, the core made of organic matter becomes a gas component such as carbon dioxide when burned out, and when this gas component is discharged out of the bearing ball, it forms excessive pores having a pore diameter of 2 μm or more in the ceramic sintered body. This leads to a shortened life. From such a point of view, it is possible to prevent generation of excessive pores by performing the degreasing step while applying pressure at a pressure higher than the atmospheric pressure.

The sintering process is slightly different depending on the matrix ceramic, but is preferably in the range of 1600 to 1900 ° C. The sintering method is normal pressure sintering, hot press sintering and atmospheric pressure sintering. Various methods such as hot isostatic pressing (HIP) can be applied. Also, when producing bearing balls, after normal pressure sintering
It is also effective to apply two-step sintering such as HIP sintering.

After the sintering step, a surface treatment is performed as necessary to form a sliding member, for example, a bearing ball.

[0030]

EXAMPLES (Examples 1 to 10, Comparative Examples 1 to 3) Matrix ceramic powder having an average particle diameter of 0.8 μm shown in Table 1 and yttrium oxide powder or aluminum oxide having an average particle diameter of 0.9 μm as a sintering aid Mix powder, maximum diameter 2
A mixed raw material powder was prepared by adding SiC particles having a particle size of μm or less in three portions at one-hour intervals and mixing them with a ball mill. When the matrix is silicon nitride,
Both yttrium oxide and aluminum oxide were added, and for other matrices only yttrium oxide was added. Next, a spherical core made of an organic material was prepared, and a compact was produced by rolling granulation and isostatic pressing. After that, the core was degreased in an atmosphere of 1.5 atm or more under the condition of 200 to 800 ° C. to burn out the core. 1600-1900 ℃ in nitrogen atmosphere
And then HIP sintering at 1600-1900 ° C. As a finishing process, surface polishing equivalent to Grade 3 or more specified by JIS is performed, and the diameter according to the embodiment is 2 mm.
Was manufactured. To bearing balls of the Examples, the proportion of the conductive imparting particles in the thickness direction R _1, the electric resistance value was measured crushing load.

For comparison, Comparative Example 1 containing no conductivity-imparting particles and having no hollow portion, Comparative Example 2 having a hollow portion and containing a small amount of the conductivity-imparting particles, Comparative Example 2, The same measurement as in the example was carried out as Comparative Example 3 in which the particles having the above-mentioned and having the conductivity-imparting particles added in an excessive amount at one time were used. The number of conductivity imparting particles in the thickness direction R ₁ was measured on an arbitrary three points in each bearing ball section, indicated by the average value. The electric resistance value was obtained by lapping the upper and lower sides of each bearing ball, placing two electrodes on the same plane, and measuring the resistance value between them at room temperature with an insulation resistance meter. The crushing load was responded by applying a compressive load using an Instron type testing machine and measuring the load at the time of destruction by a measuring method according to the old JIS standard B1501. In addition, each measured value is obtained by preparing 100 bearing balls according to each example and the comparative example, and indicating the average value. Table 1 shows the results. Arzil of the matrix ceramic is a mixture of zirconium oxide (zirconia) and aluminum oxide (alumina) at a weight ratio of 7: 3. Also, the bearing balls according to each of Examples and Comparative Examples 2-3 having a hollow portion radius R ₀ is a 1 mm, R ₁ was 0.6 mm.

[0032]

[Table 1]

As can be seen from Table 1, the hollow ceramic sintered body (bearing ball) according to the example of the present invention had an electric resistance value in the range of 10 ⁹ to 10 ² Ω · cm. Further, not shown in the table, but for any of R _1, the distance of the conductive imparting particles to each other on the R ₁ was between 0~10μm both. Also,
The crushing loads were all over 19 kN. In contrast, Comparative Example 1 in which no conductivity-imparting particles were added and Comparative Example 2 in which only a small amount of conductivity-imparting particles were added had an electric resistance value of 10 ¹⁰
No improvement was observed in the insulating property when it was Ω · cm or more. On the other hand, in Comparative Example 3 in which the conductivity-imparting particles were excessively added at once, the crushing load was considerably reduced to 11 kN, though the electric resistance was low. This is presumably because the excessive addition of the conductivity-imparting particles reduced the strength of the silicon nitride sintered body more than necessary.

(Examples 11 to 20, Comparative Examples 4 to 6) Next, using the bearing balls of Examples 1 to 10 and Comparative Examples 1 to 3, the present invention is applied to a spindle motor for rotating a hard disk drive as an electronic device. The presence or absence of a defect due to static electricity and the rolling life were measured. The bearing member of the spindle motor has a rotating shaft and a ball receiving part made of SUJ2 bearing steel.
One bearing ball was used.

The presence or absence of a defect due to static electricity was determined by whether or not the hard disk drive functions in the same manner as before the operation when the motor was rotated at 6000 rpm and operated continuously for 200 hours. The rolling life was 6000 rpm and 900
It was confirmed by the presence or absence of breakage of the bearing balls when the motor was rotated at 0 rpm and operated continuously for 200 hours. For each of the examples and comparative examples, 100 units were manufactured, and the above-described measurement was performed. Table 2 shows the results.

[0036]

[Table 2]

As can be seen from Table 2, no failure due to static electricity was observed in the bearing balls of Examples 12 to 15 and Examples 17 to 20 using the bearing balls. For Example 11 and Example 16, the electric resistance value was 10 ⁷ Ωcm
From the above relatively high levels, about 1 to 2 out of 100 units were confirmed to be defective due to static electricity. On the other hand, in Comparative Examples 4 and 5, the electric resistance value was unreasonably high at 10 ¹⁰ Ω · cm or more, so that 5 or more out of 100 units had problems. Further, regarding the rolling life, Examples 11 to 14, Examples 16 to 1
8, 6000 rpm, 9000 for Example 20 and Comparative Examples 4-5
No breakage of the bearing ball was confirmed at any rpm. This shows that even with the hollow portion as in the present invention, the bearing ball for electronic equipment shows sufficiently excellent sliding characteristics (rolling life).
The reason for this is that the conductivity-imparting particles have a good dispersion state on R ₁ and thus the conductivity-imparting particles function only to lower the electric resistance value and do not significantly affect the lowering of the sliding characteristics. Conceivable. In addition, it is considered that this is because centrifugal stress generated when high-speed rotation is performed is small due to the fact that it has a hollow portion and is lighter than one that does not have a hollow portion.

On the other hand, when the number of particles for imparting conductivity was large as in Comparative Example 6, the bearing balls were broken even at 6000 rpm. If the disk is damaged in this manner, the disk cannot be driven to rotate, of course, so that the reliability of the electronic device is reduced. The proportion of such Given a defect and rolling life by static electricity as bearing balls electronics conductivity imparting particles in R ₁ can be said to preferably in the range of 20-50%.

(Examples 21 to 24, Reference Example 1) Next, R ₁
The distance between the conductivity-imparting particles above will be discussed. Creating a cohesive portion of the conductivity-imparting particles by changing the method of adding the conductivity imparting particles into the raw material powder, the table the rate at which the distance and the conductivity-imparting particles of the conductivity-imparting particles to each other on the R ₁ is in contact 3 A bearing ball modified as described above was produced. Incidentally, the matrix of the bearing balls of silicon nitride, conductivity imparting particles with the following SiC powder maximum diameter 0.7 [mu] m, the radius R ₀ is 1 mm, conductivity imparting particles on R ₁ together with the unifying R ₁ to 0.7mm The proportions were adjusted to average 30% (both in the range of 25-35%). The crushing load of the bearing balls of each of the examples was measured in the same manner as in the example 1. Further, using the same method as in Example 11, 90
The presence or absence of breakage of the bearing ball when rotated at 00 rpm and 12000 rpm was confirmed. Table 3 shows the results.

[0040]

[Table 3]

As can be seen from Table 3, the ratio (%) of contact between the conductive particles on R ₁ is 0 to 40% and 50% or less. No damage to the bearing ball was observed even after the rotation. In contrast, for Example 24 exceeding 50%, no damage was confirmed at 9000 rpm, but 12000 rp
In the case of m, although not completely damaged, slight cracking was confirmed, so it was described as "somewhat". Reference Example 1
Damaged even 9000rpm was confirmed in a state in which a conductivity-imparting particles on R ₁ are in contact all as indicated in. From this, the distance between the conductivity imparting particles is 0 to 10 μm,
State conductivity imparting particles come into contact with each other can be said that it is preferably not more than 50% in R _1.

(Examples 25 and 26, Reference Example 2)
Confirm the effect of the ratio of R _{1 to} R ₀ . Example 22
Using the same bearing balls (radius R ₀ = 1 mm) as in Example ₁ and changing the value of R ₁ as shown in Table 4, the same measurement as in Example 22 was performed. Table 4 shows the results.

[0043]

[Table 4]

[0044] Table As can be seen from 4, the values of R ₁ as a had a hollow portion was found not to influence the sliding properties, if 50% or more of R _0. On the other hand, in Reference Example 2 in which the value of R1 was less than 50% of _R0 , it was found that the strength was insufficient because the thickness of the hollow ceramic sintered body was small. This is presumably because the thickness is small, and furthermore, the state in which the conductivity-imparting particles are in contact with each other easily exceeds 50% as a result.

(Examples 27 to 30) Next, bearing balls were prepared in which the maximum diameter of the conductive particles was changed as shown in Table 5. For such a bearing ball, Example 2
As in the case of No. 1, the presence or absence of breakage of the bearing ball at 9000 rpm and 12000 rpm was confirmed. The matrix of the bearing ball is made of silicon nitride, and the conductivity imparting particles are made of SiC particles. The radius R ₀ is 1 mm (diameter 2 mm), R ₁ is 0.7 mm, and the ratio of the conductivity imparting particles on R ₁ is 20% on average. (All within the range of 15 to 25%).

[0046]

[Table 5]

As can be seen from Table 5, when the high-speed rotation of 10,000 rpm or more is performed, if the maximum diameter of the conductivity-imparting particles is larger than 5 μm, the conductivity-imparting particles become the starting point of destruction. Therefore, the maximum diameter of the conductive particles is 5
It can be said that it is preferably at most 3 μm, more preferably at most 3 μm.

(Examples 31 to 50) Next, when the matrix ceramic is silicon nitride, Example 2 (15% of the conductivity imparting particles), and when the matrix ceramic is zirconium oxide, Example 8 (Conductivity imparting). Particle ratio 25
%), The electrical resistance value and the crushing load when the material of the conductivity imparting particles is shown in Table 6 were measured.

[0049]

[Table 6]

When the particles were changed to the conductivity-imparting particles shown in Table 6, the electric resistance values of Examples 31 to 40 in which the matrix was silicon nitride were within the range of 1 × 10 ⁶ to 4 × 10 ⁶ Ω · cm, and were crushed. Load is 23
It was in the range of 2626 kN. Similarly, for Examples 41 to 50 in which the matrix is zirconia, the electric resistance value is 6 × 10 ⁴ -1.
× 10 ⁵ Ω · cm, and the crushing load was in the range of 20 to 24 kN.
Thus, it was found that even if the material of the carbide was changed, the electric resistance value and the crushing load exhibited excellent characteristics. Thus, it has been found that the hollow ceramic sintered body of the present invention is suitable for a sliding member for electronic equipment, particularly a bearing ball for electronic equipment. The distance between the conductive imparting particles, by devising the like ratio of R ₁ to the radius R _0, it is possible to further improve the sliding properties.

[0051]

According to the present invention, the electric resistance value can be controlled by including a predetermined amount of the conductivity imparting particles in the hollow ceramic sintered body having a hollow portion as in the present invention.
By applying such a hollow ceramic sintered body of the present invention to, for example, a bearing ball which is a sliding member for electronic equipment, it is possible to effectively suppress the occurrence of problems due to static electricity. Further, it is possible to further improve the sliding characteristics of the bearing ball by controlling the distance of a conductivity-imparting particles of the above R _1, the ratio of R ₁ in the radius R _0. Such a motor for an electronic device using the bearing ball of the present invention can realize stable high-speed rotation and improve the reliability of the electronic device.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a bearing ball which is a hollow ceramic sintered body of the present invention.

[Brief description of reference numerals]

1: ceramic surface layer 2: hollow part R ₀ : radius R ₁ : thickness of ceramic surface layer in radius R ₀

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F16C 33/44 C04B 35/58 102Y (72) Inventor Yukihiro Takenami 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa F-term in Toshiba Yokohama Office (reference) 3J101 AA02 BA03 BA10 EA41 EA42 EA44 EA72 FA11 4G001 BA03 BA09 BA32 BB03 BB09 BB32 BC13 BC24 BC43 BC56 BD12 BD13 BD22 BE31 4G030 AA12 AA17 AA36 AA48 CA07 GA22 GA29 4G031 AA08 AA12 AA29 AA37 AA38 BA02 BA19 CA07 GA06 GA12

Claims (12)

[Claims] 1. A ceramic sintered body having a hollow portion therein, wherein a conductivity-imparting particle is present on a straight line in a thickness direction of the ceramic sintered body when the straight line is drawn in the thickness direction of the ceramic sintered body. Hollow ceramic sintered body. 2. The hollow ceramic sintered body according to claim 1, wherein the sintered body has an electric resistance of 10 ⁹ to 10 ² Ω · cm. 3. The distance between the conductive particles is 0 to 10 μm.
3. The hollow ceramic sintered body according to claim 1, wherein the sintered body is in the range of: 4. The hollow ceramic sintered body according to claim 1, which has a spherical shape. 5. The hollow ceramic sintered body according to claim 1, wherein the ceramic sintered body mainly contains at least one of zirconium oxide, aluminum oxide and silicon nitride. . 6. The method according to claim 1, wherein the conductivity-imparting particles are Si, Ti, Nb, Hf, W, Mo, T
The hollow ceramic sintered body according to any one of claims 1 to 5, wherein the sintered body is at least one of carbides or nitrides of a, Cr, Zr, Mn, and B. 7. A sliding member using the hollow ceramics sintered body according to claim 1. 8. The sliding member according to claim 7, wherein the sliding member is for an electronic device. 9. A ceramic bearing ball having a hollow portion therein, characterized in that when a straight line is drawn in the radial direction, 5 to 60% of the conductivity imparting particles are present on the straight line. 10. The ceramic bearing ball according to claim 9, wherein the ceramic bearing ball has an electric resistance of 10 ⁹ to 10 ² Ω · cm. 11. The ceramic bearing ball according to claim 9, wherein the size of the hollow portion is 1/2 or less with respect to the radial direction of the ceramic bearing ball. 12. The ceramic bearing ball according to claim 9, wherein the ceramic bearing ball is applied to a sliding member for an electronic device.